Understanding the Impact of Eczema, Psoriasis on Risk of Severe Mental Illness

A higher risk of severe mental illness was seen among patients who had atopic eczema or psoriasis when their outcomes were compared with a matched control population, according to analyses of electronic health records from the UK Clinical Practice Research Datalink (CPRD) GOLD that took place from January 2, 1997 to January 31, 2020.

Study findings were published in Clinical Epidemiology.

Each of the adult patients in the study cohort was matched with up to 5 healthy adults. There were 1,023,232 patients in the atopic eczema cohort matched with 4,908,059 healthy controls and 363,210 and 1,801,875, respectively, in the psoriasis groups.

“Existing research exploring associations between atopic eczema or psoriasis, and severe mental illness (ie, schizophrenia, bipolar disorder, other psychoses) is limited, with longitudinal evidence particularly scarce,” the study authors wrote. “Therefore, temporal directions of associations are unclear. We aimed to investigate associations between atopic eczema or psoriasis and incident SMI among adults.”

The overall greater risk of severe mental illness ranged from 17% among those with psoriasis (HR, 1.17; 95% CI, 1.12-1.22) to 26% within the study participants who had atopic eczema (HR, 1.26; 95% CI, 1.18-1.35). This risk, however, did not persist among the atopic eczema cohort (HR, 0.98; 95% CI, 0.93-1.04) and dropped to 14% among the psoriasis cohort (HR, 1.14; 95% CI, 1.05-1.23) after accounting for the following mediators: comorbidity burden, smoking status, harmful alcohol use, and body mass index.

Median (IQR) follow-ups were similar among the study groups: 5.5 (2.2-10.4) years for those with atopic dermatitis and 4.8 (1.8-9.6) for their matched controls, and 5.9 (2.3-11.5) years for those with psoriasis and 5.9 (2.4-11.4) among their healthy counterparts. More than half of all participants were female patients, the most common body mass indexes were normal (18.5-24.9 kg/m²) or overweight (25.0-29.9 kg/m²) ranges, and most patients self-identified as White—although the investigators did highlight that “more than half of individuals in both cohorts had missing ethnicity data, therefore ethnicity was only considered in sensitivity analyses.”

A subanalysis of outcomes between those with severe atopic eczema and moderate disease showed comparable risks of severe mental illness:

For severe disease, there was a 56% higher risk (HR, 1.56; 95% CI, 1.21-2.01) and for moderate disease, 61% greater risk (HR, 1.61; 95% CI, 1.50-1.73).

This finding marks a significant difference with the patients with psoriasis. Among that group, the risk of severe mental illness was 28% for those with mild psoriasis (HR, 1.28; 95% CI, 1.19-1.37), but no evidence pointed to a higher risk among those with moderate/severe psoriasis (HR, 0.97; 95% CI, 0.69-1.35).

Calendar period and sex (for this study, 1997-2003, 2004-2009, 2010-2015, 2016-2020) did not influence mental illness outcomes among both patient groups, but a potential link was seen from age. There were 23% and 37% higher risks seen with ages 30 to 39 and 40 to 59 years, respectively, among the adults with atopic eczema and evidence of a potential link between severe mental illness and all age groups with psoriasis excepting those aged 30 to 39 years (P = .01).

The study investigators highlighted there were minimal effects from the other potential mediators on links between severe mental illness and atopic dermatitis or psoriasis.

“To our knowledge, this is the largest study to investigate temporal associations between atopic eczema or psoriasis and incident severe mental illness in adults,” they concluded. “The CPRD dataset used is broadly representative of the UK population, suggesting our results are generalizable to the UK population with atopic eczema or psoriasis.”

Another strength of their findings is that they echo current, albeit limited, literature showing temporal associations between atopic disorders or psoriasis and severe mental illness. However, complete generalizability is limited by potential selection bias and that the authors’ definition of disease severity may have led to disease misclassification.

Reference

Adesanya EI, Henderson AD, Matthewman J, et al. Severe mental illness among adults with atopic eczema or psoriasis: population-based matched cohort studies within UK primary care. Clin Epidemiol. 2023;15:363-374. doi:10.2147/CLEP.S384605